Telephone system.



CLARENCE B. FOWLER, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE SYSTEM.

arissa.

Application filed September 25, 1917.

To all whom it may concern:

Be it known that I, CLARENCE B. FOWLER,

a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone systems, and more particularly to such systems of the central energy type in which the busy or idle cnditi0n of a telephone line is determined. by the, presence or absence of a definite potential at the test terminals of the jacks in which the lines terminate.

In systems of this character employing poly-station telephone lines where the called party is on the same line with the calling nut and the answerin )lu of the cord U l C circuit is in the line jack of such a line, a busy test relay connected with the tip or testing strand of the calling end of the cord circuit must operate upon the engagement of this testing conductor with the test terminal of another jack connectedwith the same line to connect a source of tone supply to the test terminals of all jacks of the line through the sleeve of the answering jack. A tone is then produced in the operators receiver connected with the testing conductor. Such a busy test is known as a reverting busy test.

In such systems, the operation of the busy test relay has not been entirely satisfactory even when employing relays especially designed and constructed for such service. It is therefore the object of this invention to provide busy testing means in which the difiiculties heretofore experienced are not encountered.

In accordance with this invention a busy test relay of ordinary construction under the conditions mentioned is more positive in operation than the relay heretofore employed, thereby insuring under various conditions of service, that the reverting busy test will at all timesbe obtained by the operator making such test.

For a more complete understanding of this invention reference should be had to the following description considered in connection with the accompanying drawing,-

wherein Figure 1 shows a cord circuit containing one embodiment of this invention; Fig. 2 shows a modification of that shown in Fig. 1; and Fig. 3 shows an ordinary poly- Speeification of Letters Patent.

Patented July 9, 1918.

Serial No. 193,102.

station telephone line. For convenience, the like apparatus of Figs. 1 and 2 are designated by the same reference characters.

It isthought that this invention will be understood from a description of the operation of the systems disclosed in the drawings, and it will therefore be so described.

Assuming that the party at station A. on the telephone line D initiates a call by removing his receiver from the switchhook, the line relay 5- is actuated to cause the lighting of the line lamp 6. The operator, upon observing the lighted condition of the line lamp (3, inserts answering plug 7 of cord circuit G into jack 8 of line D, whereupon the cut-off relay 9 and supervisory relay 10 are operated, the former disconnecting the line relay from the line and causing the effacement of the line lamp, and the operation of the latter preventing the lighting of answering supervisory lamp 11, which is now short-circuited through the alternate contact of answering supervisory relay 10.

The operator may now actuate listening key 15, thereby connecting the operators telephone set 16 with the talking conductors of the cord circuit. The actuation of the listening key also opens contact 17 re moving a short circuit from resistance coil 18, which is thereupon included in the tip or testing conductor 19 in series with the winding 20 of the repeating coil 21. The actuation of this listening key also closes contact 22, preparing a. circuit for the connection of a source of tone supply to the sleeve of the jack with which the answering plug is connected, and connects a busy test relay 23, which is common to a plurality of cord circuits through contact 2% with the testing conductor 19. When so connected the relay 23 is in parallel with the resistance coil 18 and winding'20 of repeating coil 21.

The operator, upon being advised that party A desires to be connected with party B, touches the tip of plug to the sleeve contact of another jack 31 of line D, in order to determine whether the line of party B is idle or busy. There is an answering jack for each station of a poly-station line and each station has a separate number, so that when the called station is on the same line with the callin station, the operator has no knowledge of this fact until after testing the line. Upon the engagement of the tip of plug 30 with the sleeve of jack 31, relay 23 'is operated over a circuit from battery through the alternate contact of supervisory relay 10, resistance 12, sleeve contacts of the answering plug 7 and line jacks 8 and 3 tip contact of the plug 30, contact 24L or 11stening key 15, and the winding of'relay 23 to ground. At the same time a click is produced in the operators receiver 38. In sys tems heretofore employed, the Winding of the repeating coil 21 has been included in parallel with the busy test relay, but since the windings of repeating coils connected 1n the talking, circuit must necessarily be or low' resistance in order to be of the highest efliciency for transmitting telephonic currents, the winding connected in calling tip conductor shunts so much current from the busy test relay that there has been considerable difficulty in providing a busy test relay which would respond under such conditions. Res stance 18, whlch is connected 1n serles with winding 20 of repeating coil 21 when the listening key is actuated, is of quite high resistance, so that when winding 20 and the coil'18 are in series and are in multiple with the winding of the busy test relay, there will be less shunting of the current from the busy test relay, In this way, the busy test relay receives a larger amount of current when testing the condition of the line wlth which the answering plug of thesame cord circuit is connected and responds much more many; In fact,'this' temporary increase of the resistance in shunt of the busy test relay while making a busy test improves the operation to such an extent that the special relays heretofore used for this purpose may be replaced by relays of ordinary construc tion. Relay 23 in operating connects a source of tonesupply 33in circuit with the operators receiver 38 to produce a tone therein. This circuit may be traced from the sourceof tone supply 33 through the contact of busy test relay 23, contact or discon nect relay 36 (common to a plurality of cord circuits) ,fcontact 22 of listenlng key 15, conductor 3 1, sleeve contacts of the answering plug 7 and the jacks 8 and 31, tip contact of plug 30, testing or tip conductor19, contact 2a of listening key 15,, induction coil winding 37 in the operators telephone set,

receiver 38, condenser 39, contact 35 of lisel ing k y W d n i llin pe s ry r ay .7, ierea ei o l. W n i 0.

and battery to ground; Upon receiving this tonein the receiver, the operator is advis ed that hfiballedparty is on thesame line wlth calling party, Thelcalled party may thenbe signaled, in any desired manner, and connections the calling and called et en 'p t esn ay also. b de eted? y desired manner.

Assuming, that the call. 1s for asubscriber on another telephone hfne slmilar to line D,

the engagement of the tipof the callinjg plug off relay of the line is operated. The called subscriber may then be signaled in any (187, sired'manner. "The removal of the receiver at the called station from its switchhook causes the operation of the calling supervisory relay 17, which opens its normal contact, removing the short circuit from about relay 45 and permitting its operation, and closes its alternate contact, short-'circuiting the lamp 456, which is thereby extinguished.

If,'while the two telephone lines are connected for conversation, should the operator in supervising the connection actuate the listening key 15, the resistance 18 will not be included in the tip conducter 19 for it is now short-circuited through the contact of relay The actuation of the listening key, while connecting the operators telephone set 16 to the talking strands of the cord circuit, also causes the operation of discon nect ma 36 over a circuit from battery from the winding of disconnect relay 36, the contact 35 of listening key 15, ring contacts of the calling plug 30 and the line jack of the'called line, out over one side'of that line through the substation apparatus and switchhook contact,back overv the other side of the line, tip contacts of the line jack and the calling plug 30, tip conductor 19, 'con tact of relay 45, and repeating coil winding 20 to ground. Relay 36, in operating, in-' trodu'ces a break in the lead through which the source of tone supply 33 is connected with the sleeve of the 'jack into which the answering plug 7 is inserted. This prevents the changing of the test potential of the jack sleeves of the calling line, so that should another operator be making a busy test on that line while the, first operator is connected with cord circuit C, the second operator will receive the usual busy' test indicatlon.

In supervising this connection, the operator after obtaining the desired information may restore the listening key to normal position, thereby disconnecting relay'36 from the cord circuit. At the conclusion of the conversation, the subscribers restore the receivers to the switchhoo'ks, causing the release of the answering and calling supervisory relays 10 and 47, which in releasing, r emove the short circuitsof the answering and calling supervisorylan ps 1 1 and L6, which' listening key of any one of thecord circuits is actuated, is connected in the tipor testing conductor in series with the repeating coil winding 20. The portion of the circuit including the common resistance 50, when connected in the tip conductor,

may be traced from the tip of the calling plug 30 through contact 51 of listening key 52, resistance 50, contact 53 of the listening key 52 and repeating coil winding 20. When the listening key 52 is actuated, the source of tone supply 33 is connected with the test terminal of the jack in which the answering plug is connected through the contact of busy test relay 23 (actuated when the tip contact of the calling plug 80 is brought into engagement with the test terminal of the busy jack), contact of disconnect relay 36, contact 54, listening key 52 and conductor 84.

It is believed that this brief description will serve to make the operation of the cord circuit of Fig. 2 clear, and that it will therefore be unnecessary to trace out in detail the complete operation. 1

What is claimed is:

1. In a telephone system, in combination, a telephone line terminating in a plurality of jacks, a cord circuit having a combined talking and testing conductor for engaging the test terminal of a ack to determine the idle or busy condition of the line, a busy test relay, a resistance coil, and a listening key actuated to connect the resistance coil in the combined talking and testing conductor and to connect the test relay with the testing conductor in parallel relation to the resistance coil.

2. In a telephone system, in combination, a telephone line terminating in a plurality of jacks, a plurality of cord circuits each having a combined talking and testing conductor for engaging the test terminal of a jack to determine the idle or busy condition of the line, a busy test relay, a resistance coil common to a plurality of cord circuits, and a listening key actuated to connect the resistance coil in the combined talking and testing conductor, and to connect the busy test relay with the testing conductor in parallel relation to the resistance coil.

3. In a telephone system, in combination, a plurality of poly-station telephone lines, each terminating in a plurality of jacks, a plurality of cord circuits, one of the cord circuits having its answering end connected with a jaok-of'one of the lines, a testing conductor for the calling end of each of the cord circuits, an operators telephone set, a listening key for the engaged cord circuit for'connecting the operators telephone set therewith, a resistance coil common to the cord circuits connected in series 'with the testing conductor of the engaged cord circuit by the actuation ofthe key, a source of tone supply, a test relay connected with the testing conductor of the engaged cord circuit in parallel with the resistance coil by the actuation of the key and responsive to the engagement of the testing conductor thereof with the test terminal of another jack of the engaged line to connect a source of tone supply in circuit with the receiver of the operators telephone set.

4. In a telephone system, in combination, a plurality of poly-station telephone lines,

eaclrterminating in a plurality of jacks, a

plurality of cord circuits, one of the cord circuits having its answering end connected with a jack of one of the lines, a testing conductor for the calling end of each of the cord circuits, an operators telephone set, a listening key for the engaged cord circuit for connecting the operators telephone set therewith, a resistance coil common to thecord circuits connected in series With the testing conductor of the engaged cord circuit by the actuation of the key, a source of tone supply, a test relay connected with the testing conductor of the engaged cord circuit in parallel with the resistance coil by the actuation of the key and responsive to the engagement of the testing conductor thereof with the test terminal of another jack of the engaged line to connect the source of tone supply in circuit with the receiver of the operators telephone set, a relay energized when the calling end of the engaged cord circuit is connected with the jack of another line, and a circuit established upon the energization of the last mentioned relay for preventing the connection of the resistance coil in the testing conductor.

5. In a telephone system, in combination, a poly-station telephone line terminating in a plurality of jacks, a cord circuit having its answering end connected with one of the jacks, a testing conductor for the calling end of the cord circuit, a repeating coil for the cord circuit having a winding connected in the testing conductor, an operators telephone set, a listening key for connecting the operators telephone set with the cord circuit, a resistance coil connected in series with the repeating coil winding by the actuation of the key, a source of tone supply, and a test relay connected with the testing conductor and in parallel with the resistance coil and the repeating coil winding upon the actuation of the key and responsive to the engagement of the testing conductor with the test terminal of another incl: to connect the soi'i'rce of tone supply in circuit Withthe Teceiver of the ope'rators telephone Set.

6. In a telephone system, in combination, a, poly-station telephone line terminating in a plurality of jacks, a 'corl circuit haying itsanswering encl connected with one of the jacks, a testing conductor for the calling end of the corclcircuit, a repeating coil for the cord circuit having a winding connected in the testing conductor, en operato'rs telephone "set, 'a listening key on cohiiect'i-iig the operators telephone set With the cord circ'uit', a resistance coil con nected in, series with the repeating coil Winding by the itctuation of the key, i source of "tone supply, a test relay connected with. the testing conductor and in parallel with the resistance coil evil-cl the repeating coil Winding upon the actuation of the key and 'rs'poxis'iv-e to the I engagement of the testing concl'ictoi' with the test term-i-nitl ,iof another jack to conmeet the source of tone supply in ':irci1it with the receiver of the 'o-peratofls telephone set, a relay in the callingencl of the cord circuit energized While the corc'l oircuitis connected with a telephone l-in'e, mid a disahling circuit established upon the energizetion off the last mentioned ielay 'tofp-r'event the connection of the resistance coil in the testing fconductor Wliertthe key is actuated.

In Witness "whereof, lhereimto "subscribe mygmime this '18-thclay of September, 'A. D; 191

enema-1: B.

Copies of this patent may be obtaihe d forjfiyef bents each, by adiiressing the Commissidiier of Patents,

Washington, D. O. i 1 

